Blast-free explosive line cutter



Feb. 9, 1960 L, BOHL EIAL 2,924,141

BLAST-FREE EXPLOSIVE LINE CUTTER Filed Aug. 5, 1957 7s 72 62 41; Q {Ya/6:5: 12 F so I 84 86 x 65 I 1:90

Ill/11111111111111 INVENTORS LELAND S. BOHL RAYMOND W. MAAs RUDOLPH B. THORNESS b3: 4%;, W AT-rvs United States Patent BLAST-FREE EXPLOSIVE LINE CUTTER Leland S. Bohl, Schenectady, N.Y., and Raymond W. Maas and Rudolph Bernhard Thorness, Minneapolis, Minn., asslgnors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application August 5, 1957, Serial No. 676,451

12 Claims. (Cl. 89-1) This invention relates to equipment-release devices, and is concerned more particularly with improvements in explosive devices for severing lines such as the load line suspended from a high altitude balloon.

An object of the invention is to provide a balloon load llne safety explosive cutter from which the blast of gases and fragments cannot escape, whereby danger to nearby balloon film, equipment or personal is eliminated.

A further object is to provide an inexpensive, easily produced safety explosive line cutter.

Furtherobjects and advantages of the invention will appear as the description proceeds.

The invention will be better understood upon reference to the following description and the accompanying drawing, wherein:

Fig. l is a central longitudinal sectional view, partly in elevation, of a line cutter constructed in accordance with one form of the invention, with a control circuit diagram.

Figs. 2 and 3 are the respective left and right end elevational views of the cutter of Fig. 1.

Fig. 4 is a sectional view taken as indicated at 4-4 in Fig. 1.

Fig. 5 is similar to Fig. 1 but shows on an enlarged scale the condition of the cutter after firing.

Fig. 6 is a sectional view taken as indicated at 66 in Fig. 5 but on a reduced scale.

Fig. 7 issimilar to Fig. l but shows a modified cutter.

Fig. 8 is similar to Fig. 7 but shows the condition of the modified cutter after firing.

Fig. 9 is a. schematic view showing a form assembled with a balloon.

Referring now more particularly to the drawing, disclosing illustrative embodiments of the invention, there isshown at 10 a cutter comprising a case 12 having a barrel 13 and formed at its rear end 14 with a small passage 16, and having at its front end 17 a tapped mouth 18 terminating inward at a shoulder 20. The barrel 13 also has an intermediate eye, indicated generally at 22, comprising a pair of holes 24 and 26 communicating with the barrel bore 28. Wiring 30 tightly embraced by a rubber or other plug such as the disc 31 and connected to a squib 32 is inserted through the mouth 18 and the passage 16 to position the plug and squib at the case end 14. A line-cutting bullet or slug 34 is inserted through the mouth 18 and is made to have a gas-tight fit with the wall of the bore 28 and is positioned adjacent the squib 32, where it is retained by friction with the bore wall.

The ends 36 of the slug 34 are recessed to provide peripheral knife-edges 38 and 40, respectively. A plug 42 is then threaded into the mouth 18 to the shoulder 20, providing a stop for arresting the flight of the impelled slug 34, the axial distance from the stop to the rearmost parts 44 of the eye holes 24 and 26 being less than the length of the slug.

The wiring 30 forms part of an electric circuit including a switch 48 and a battery 50.

The device 10 is assembled with a line such as a balcutter of either loon load line 54 passing through the eye 22, so that a portion 56 of the line is in the path of the slug 34. The line 54 is adapted to have a friction fit in the eye holes 24 and 26 to enable the line to support the device 10. Closing of the switch 48 fires the squib 32, impelling the slug 34 so that the front edge 38 of the slug slices the line 54 at the ends of the intermediate portion 56, which, as shown in Fig. 5, becomes jammed between the slug and the plug 42. The slug 34 thus obstructs and maintains closed the eye holes 24 and 26, and the plug 31 closes the passage 16,.blocking escape of the blast gases and squib fragments indicated as a whole at 58. The case 12 is strong enough to preclude rupture from the explosive pressures. Timed line cutters carried on prematurely descending balloon flights have been a potential j danger to people finding the equipment. This danger is ting end, thereby eliminating the possibility of improperassembly of the parts. However, if desired, only the end to be disposed foremost may be formed as a cutting end.

Once the line 54 is severed while the balloon is aloft, the weight of the load will pull the lower part of the line out of the barrel eye hole 26, or will pull the device 10 off the upper part of the line, so that the load is freed from the balloon.

A modified cutter is shown at 62 and comprises a case 64 whose barrel 65 may be a piece of standard gas pipe that is, pipe stocked by dealers are readily purchaseable,

and in common use in plumbing and for other consumer and industrial purposes, such as water or gas pipes, having an eye 66, comprising holes 68 and 69 and the communicating bore 70, for the passage of the line 54. The pipe ends 72 are externally threaded for engagement with end closures which are preferably standard caps 74 and 76, that is, pipe caps stocked by dealers and readily purchaseable for use with standard pipe 65. One of the caps for the purpose of the invention is bored at 78 to accommodate the squib wiring 30. The cutting slug or bullet of this form of the invention is indicated generally at 80 and comprises a pair of preferably identical cup-like pieces 82 and 84 of bored drill rod or other suitable material, having closed ends 86 and rims having knifeedges 90 and 92 frictionally engaging the wall of the barrel bore 70. The friction fit is obtained by expanding the rims to size. A neoprene or other suitable disc gasket 93, sandwiched between the closed ends 86, completes the slug 80, which is readily inserted in the barrel 65 so as to leave clearance for passage of the line 54 through the eye 66. A squib 94 is slidably or loosely fitted in the rear piece 84, with the squib wiring 30 passing through the cap hole 78 anda plug 95 similar to the plug 31, and the caps 74 and 76 applied to complete the assembly of the cutter 62. The gasket 93 has a substantially sliding fit in the wall of the bore 78. The cutter 6-2 is then mounted on and held by the line 54 in the manner noted above.

On closing of the switch 48, the squib 94 is fired, impelling the slug 80 forward so that the gasket 93 is compressed into gas-tight sliding engagement with the wall of the bore 78, the cutting edge 90 of the forward piece 82 slices the line 54 in the manner noted above, and the piece finally impinges against and is upset as at 96 (Fig. 8) by the conical bottom 98 the of the interior of the cap 74, with the line slice (not shown) trapped. This latented Feb. 9, 1960 93 is at the rear of the eye holes 68 and 69, thereby blocking escape through these holes of the explosion gases and squib fragments, both indicated generally at 100, from the eye holes. The function of the plug 95 is the same as that of the plug 31. The case 64 is of suflicieut strength to preclude rupture by the explosion. The cutter 62 accordingly possesses the safety advantages of the cutter 10.

The cutter requires precision manufacture in order to insure against escape of gas between the slug and the barrel. The cutter 62 lends itself to substantially lower manufacttu'ing cost, employing as it does standard pipe and end caps, and to more rapid assembly. Standard pipe of a given size may vary somewhat in inside diameter from batch to batch. However, asnoted above, the slug pieces 82 and 84 can be easily made to fit to provide the friction needed to hold the slug in the desired position preparatory to firing, and the firing 'expands the gasket 93 diametrically to the desired gastight fit, so that there is no necessity for precision manufacture of the cutter 62.

With each type of cutter the gases and squib fragments remain trapped under pressure in the cannon.

An illustrative installation of the invention is shown in Fig. 9, wherein the load line 54 from a balloon 104 extends through and may frictionally support a cutter Ill or 62 below which the line suspends a parachute 106 and a load 108 which may include among other things the switch 48 and battery 50.

While a preferred embodiment has been described in some detail, it should be regarded as an example of the invention and not as a restriction or limitation thereof as changes may be made in the construction and arrangement of the parts without departing from the spirit and scope of the invention.

' We claim:

1. In an explosive safety line cutter, a barrel having a pair of holes forming with the barrel bore a transverse eye to receive a line, a squib in the barrel and rearward of the eye, a bullet member between the eye and the squib and having a front peripheral line-cutting edge engaging the bore wall, the barrel having a stop confronting a forwardly facing part of said member, and means between the squib and edge for transmitting the pressure of the squib explosion gas to said member, said means including a soft gasket out of gas-tight contact with the bore wall and deformable by the pressure of the squib explosion gases into gas-tight contact with the bore wall, the distance between the gasket and the holes exceeding the distance between the stop and said part of the bullet, whereby the explosion gases will not be accessible to either hole.

2. The structure of claim 1, characterized in that said edge is of greater diameter than the remainder of said member to minimize friction.

3. In an explosive safety line cutter, a barrel having holes forming with the barrel bore an eye to receive a line, a bullet in the bore rearward of the eye and comprising relatively rigid front and rear members and a soft rubber gasket sandwiched between and arranged to be forced by the members into gas-tight engagement with the bore wall when the bulletis impelled, the front memher having a peripheral knife-edge frictionally engaging the wall rearward of the holes, a squib rearward of a rearwardly facing part of the bullet, a stop arranged to engage a forwardlyfacing part of the from member to arrest the impelled bullet on cutting of the line, the distance from the periphery of the gasket to the holes exceeding the length of the bullets stroke, whereby access of the explosion gases to either hole will be blocked.

4. The structureof claim 3, characterized in that except at the knife-edge the front member fits loosely in the barrel.

5. The structure of claim 3, characterized in that the portions of the members contiguous to the gasket are of less diameter than the gasket. I

6. The structure of claim 3, characterized inthat the knife-edge is at the front end of the front member.

7. The structure of claim 3, characterized in that the knife-edge is at the front end of the front member and of larger diameter than the remainder of the front member.

8. The structure of claim '3, together with means for closing the bore rearward of the squib, the'closing means comprising an inwardly projecting forwardly facing annular seat defining a reduced passage, a rubber washer between the seat and the squib, and wiring connected to the squib, embraced by the washer, and extending through the passage, the washer being of larger diameter than the inner end of the passage so as to be forced against the seat by the explosion gases to block escape of the gases through the passage.

9. The structure of claim 3, characterized in that the rear member cooperates with the knife-edge on the front member and with the bore wall to hold the bullet in position until the squib is fired.

10. The structure of claim 3, characterized in thatthe front member is cup-shaped and the closed end of the front member is adjacent the gasket.

11. The structure of claim 3, characterized in that the members are identical, whereby the bullet cannot be introduced into the barrel wrong end first.

12. The structure of claim 3, characterized'in that the squib is rearward of a rearwardly facing part of said rear member.

References Cited in the file of this patent UNITED STATES PATENTS 2,346,494 Leland Apr. 11, 19:44 2,581,645 Frieder et a1. Jan. 8, 1952 2,616,748 Hight Nov. 4, 1952' 2,755,550 Benjamin July 24, 1956 2,756,948 Winzen et al. July 31, 1956 2,780,428 Moran Feb. 5, 1957 2,783,712 Smith Mar. 5, 1957 I 

